It is known that the use of the metal electrowinning and electrorefining process dates back to the 1860's. This technology has further developed to date, where, with the advent of the solvent extraction technology, anodes bear a copper bar to conduct the current, comprising the positive anode for electrowinning purposes.
Two assembled systems have prevailed to date, at the joint between the bus bar-body and the anode, one known as RSR method, and the other known as the Royston method, which correspond to the two companies that developed these methods over two decades ago.
The aforementioned systems are briefly described below:                a) RSR method (see FIGS. 1 and 2): the copper support bar (1), has a slot (2) throughout its straight 6-12 mm wide×199 mm deep×940 mm long portion (R), into which the laminated plate (3) is inserted. A coating (4A) has been previously made, (FIG. 3) on the copper support bar (1) with a Pb=52%; Sn=45%; Sb=3% alloy, and the slot (2) has been filled with the same alloy (4B); being later soldered to each other (support bar and lead plate), by solder, Pb=94%; Sb=6%; and finally, the entire head of the anode, that is the bus bar, the solder zone and 50 mm, approximately, of the sheet below the solder zone, is covered with a electrowinning deposit of pure lead of up to 0.75 mm. of thickness.        b) Royston method (see FIG. 5): the entire perimeter of the copper support bar (8) is coated with a lead-antimony-based alloy (7), preferably 6% Sb, at least 6 mm thick, and the sheet (10) is later attached to the coating (7) by using solder (9), of an alloy identical to that of the peripheral coating.        
The manufacture of anodes through the aforementioned methods, in practice, has shown different mechanical and structural deficiencies over the past two decades, which may be summarized as follows:                I).—An anode produced using the Royston system has poor conductivity, because the sheet is not directly soldered to the copper bar, but to its coating, and        II).—in the RSR system, structural distortion in electrowinning processes, and corrosion through the electrowinning lead coating on the copper bar, causes 1.—structural distortion, serious warping problem (anode concave bending) with subsequent occurrence of short-circuits; and 2.—contact problems and, eventually, bar-plate detachment due to corrosion.        The RSR-like joint system shows better conductivity, but it clearly makes apparent, in turn, the conceptual failure of the anode assembly method, which causes this system to cause such a negative bending, of great technical and economic significance to mining users, which, due to process replacement, must be stopped, causing refinery productivity to drop. The RSR system shows significant corrosion on the anode head within the first year of operation, from the destruction of the 0.75 mm thick pure lead electrowinning deposit resulting from the solder on the copper bar that acts as an adhesive element.        
There is also the system disclosed in Chilean patent CL42634, which refers to an assembly and construction method for anodes used in electrowinning processes, comprising a copper bus bar in which a slot whose thickness is 0.12 mm more than the thickness of the lead bar that will be fitted into it has been previously milled. The copper bus bar is pre-coated by being submerged in an alloy sheet, preferably Lead between 25% and 27.5%, Bismuth between 25% and 27.5% and between 45% and 50% of Tin, all at 170° C. Then, the bar is moved to the assembly table where the slot is filled with the same cast alloy and at the same temperature, and the lead sheet is immediately introduced. The copper bar starts to cool down while the lead sheet at the joint area starts to heat. After a short period of time, a thermal balance between both bodies is established at 135° C., and both start to cool down from that temperature, their expansion being identical.
When the temperature of the set at the joint area has reached 100° C., reinforcement solder is applied to the area on both sides. The solder consists of a rod solder bead between the copper bar and the lead sheet walls, which alloy is lead-bismuth, with up to 55% of bismuth. With this system copper bar bending is prevented.